The invention relates to an elevator security system, in particular a warning system for passengers in proximity of landing doors.
An elevator is usually mounted in a shaft of a building. Along such a shaft, there are a number of landings allowing access to the shaft from different floors of the building. The elevator includes a car, a counterweight, a load bearing member, a drive unit, and landing doors. The car and the counterweight are movably suspended in the shaft. The load bearing member is associated with the car, the drive unite, and the counterweight. The drive unit drives the load bearing member and, thus, moves the car and the counterweight in the shaft up and down in opposite directions.
The elevator is configured to stop at landings such that passengers can enter or leave the car. Unless a car is positioned at a landing, the landing doors are closed and prevent passengers from entering the shaft. A certain landing door only opens if the car is positioned correctly behind that landing door and if a passenger requested to enter or leave the car at that landing door. In most elevators, the car has a car door which only opens if an adjacent landing door opens. Usually the car door and the adjacent landing door are coupled such that only one door drive is necessary, and that the car door and the landing door open simultaneously.
Even though the landing doors prevent passengers from entering the shaft when the car is not positioned correctly behind a certain landing door, fatal entries through landing doors into the shaft occur. In many elevators, landing doors can be opened from the landing with a key, for example, with a three-square socket wrench. Technicians need to enter the shaft for revision or for maintenance of the elevator, but anybody having a suitable key at hand can enter the shaft from the landing.
In order to prevent unauthorized entries, WO 96/35630 A1 discloses an elevator landing door monitoring system. At least one detector is positioned on the elevator shaft at a respective location generally opposite each landing door without direct contact therewith. If the monitor detects that the landing door is open and no car is present, the monitor produces an alarm signal. The alarm signal is sent to a control circuit that takes the elevator out of service and generates audible and visual alarms.
Even with elevator landing door monitoring systems as described in WO 96/35630 A1, fatal entries through landing doors occur.